Meter provers and flow proving components use a known traceable volume under actual operating conditions to calibrate and/or verify the performance of flow meters. A SVP (Small Volume Prover) or piston prover can be employed to accurately (e.g., 0.02% tolerance) measure displaced volume in a fluid flow process and calibrate the flow measurement device employed in a custody transfer (e.g., pipe lines, etc.) or legal metrology applications. Small volume provers generally include a precisely honed cylinder with sensors positioned at key locations for detecting the beginning and ending of a piston stroke. The volume of the stroke can then be employed to determine or verify the volume measured by the flowmeter under test.
Conventional small volume provers for calibrating a liquid flow sensor with respect to the measurement of a fixed volume typically employ a drive-end used to pull the piston back to the start position. A typical drive train can include an electric motor with a chain or belt, or can be hydraulically or pneumatically driven. This requires multiple parts to function. The inherent upstream and downstream shaft requires high pressure seals for good functionality in such designs. Additionally, these shafts increase the total size of the small volume prover (SVP). This is a serious problem in many applications because there are often rigid size constraints for proper application of the small volume prover. Furthermore, prior art methods require a number of parts that make stocking and maintenance untenable. The multitude of parts required in such prior art designs also negatively influences the reliability of the system.
Based on the foregoing, a need exists for an improved small volume prover apparatus and method for measuring flow rate. A need also exists, for an improved drive end mechanism for small volume provers to minimize the number of parts, reduce the device footprint, and minimize the number of seals as will be described in greater detail herein.